Quoted from nandemoguy:
It may sound funny, but a good place to check is vpforums.org. These guys recreate real machines in a virtual format and often times have done this work. if not in vector, they will have very high quality scans of full plastics sets included with the tables. And everything is free too so its a really good resource.
Aside from plastics you can often get high quality scans or vector art of playfields as well.
Ok, I didn't want to say anything before I finish it but over the holidays I've been putting together a website to help the cause.
It's a website where users will be able to upload pinball assets such as playfield scans, digitized artwork, even modded artwork, etc, etc. It is organized by pinball machine(WOZ, TZ, etc), Asset type(playfield, cabinet, plastics art, etc.) and also by origin(high res scan, digitized, custom, etc.) and has a comments/rating system.
Since I started in the hobby I noticed it was a huge need, as it took me foreeeever to find a scan for my grand lizard restoration. I noticed everyone just links to forum posts, etc but there's no centralized place to look for stuff which currently makes it very hard to find anything.
I already have the pieces in place and have it up and running but having hosting issues that need to resolve first.
It will be up for beta soon to see if it catches up I'll keep you guys posted!